228 The habits of a Species of Ptyclus. 
the Aphrophora secretes or emits the froth from its body. 
Thus Dr. Sharp summarizes the older opinion in the 
following words:—“. . When in the immature stages, 
certain of them [Cercopidx] have the art of emitting the 
liquid in the form of bubbles which accumulate round the 
insect and conceal it” (l.c. p. 577). Professor Morse shows 
that when the insect is cleared from the bubbles and 
placed on its food-plant, “it will crawl quite rapidly along 
the stem ... , stopping at times to pierce the stem for 
the purpose of sucking the juices within, and finally 
settling down in earnest, evidently exerting some force in 
thrusting its piercing apparatus through the outer layers, 
as shown by the firm way in which it clutches the stem 
with its legs. After sucking for some time, a clear fluid 
is seen to slowly exude from the posterior end of the 
abdomen, flowing over the body first and gradually filling 
up the spaces between the legs and the lower part of the 
body and the stem upon which it rests... . During all 
this time not a trace of an air-bubble appears; simply a 
clear, slightly viscid fluid is exuded, and this is the only 
matter that escapes from the insect... . This state of 
partial immersion continues for half-an-hour or more. . 
Suddenly the insect begins to make bubbles by turning 
its tail out of the fluid, opening the posterior segment, 
which appears like claspers, and grasping a moiety of air, 
then turning the tail down into the fluid and instantly 
allowmg the enclosed air to escape. . . . These movements 
go on at the rate of seventy or eighty times a minute. 
At the outset the tail is moved alternately to the right 
and left in perfect rhythm, so that the bubbles are dis- 
tributed on both sides of the body, and these are crowded 
towards the head till the entire fluid is filled with bubbles, 
and the froth thus made runs over the back and around 
the stem.” Many other interesting facts and observations 
are recorded in this paper which should, I think, be repro- 
duced in a more accessible form, together with the simple 
but entirely adequate illustrations. The probability of 
some accessory aid to respiration by means of thin-walled 
leaf-like appendages is also discussed. The whole problem 
of the respiration of the msect enclosed in its mass of 
froth would be a fascinating subject of inquiry. The mere 
contemplation of it is enough to bring home the utter 
improbability of the older view as to the origin of the 
included gas.——K, B, PouLron. 
